Electric storage apparatus

ABSTRACT

A battery includes an output terminal, an electric storage device, a relay connected to the output terminal and the electric storage device, and a monitoring apparatus including a detector and a controller, the detector being configured to detect a variation value corresponding to an amount of charge of the electric storage device, the controller receiving an engine activation signal and switching a state of the relay to a closed state. If an engine is not started, the controller switches the state. of the relay to an open state.

The present application is a Continuation Application of U.S. patentapplication Ser. No. 15/602,719, filed on May 23, 2017, which is aContinuation Application of U.S. patent application Ser. No. 15/268,283,filed on Sep. 16, 2016, now U.S. Pat. No. 9,701,207 B2, issued on Jul.11, 2017, which is a Continuation Application of U.S. patent applicationSer. No. 14/816,769, filed on Aug. 3, 2015, now U.S. Pat. No. 9,463,699B2, issued on Oct. 11, 2016, which is a Continuation Application of U.S.patent application Ser. No. 14/048,789, filed on Oct. 8, 2013, now U.S.Pat. No. 9,165,736 B2, issued on Oct. 20, 2015, which is based on andclaims priority from Japanese Patent Application No. 2012-225832, filedon Oct. 1, 2012 and Japanese Patent Application No. 2013-187835, filedon Sep. 11, 2013, the entire contents of which are incorporated hereinby reference.

FIELD

The present invention relates to a technology for reducing powerconsumption in an electric storage apparatus while power supply to anelectric load is halted.

BACKGROUND

A battery is installed in a vehicle for supplying power to a starter tostart an engine. The battery may also be used as a power source forsupplying power to various on-vehicle devices. The battery is charged byan electric generator when the engine is running, for example, duringdriving. In contrast, the battery is not charged when the engine isstopped. A state of charge of the battery decreases if the power isbeing supplied to the on-vehicle devices or a dark current exists. Thestate of charge of the battery may decrease to a level at which theengine cannot be started, i.e., the battery may run out.

There is a known technology (for example, JP-A-2006-327487) for shuttingdown a power supply route for supplying power to an on-vehicle device,which consumes a dark current, when a battery voltage of a vehicle, theengine of which has stopped, reaches a predetermined value.

SUMMARY

The following presents a simplified summary of the invention disclosedherein in order to provide a basic understanding of some aspects of theinvention. This summary is not an extensive overview of the invention.It is intended to neither identify key or critical elements of theinvention nor delineate the scope of the invention. Its sole purpose isto present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented later.

In a known technology, a relay that shuts down the power supply routefor supplying power is provided outside the battery. A system outsidethe battery is configured to monitor the battery voltage and shut downthe relay based on the result of the monitoring. In other words, in theknown technology, the system outside the battery is required to shutdown the relay, and thus a communication means between the battery andthe system outside the battery is necessary. This is an example ofdisadvantages of the known technology.

This specification describes a technology in which the electric storageapparatus itself controls the amount of charge thereof independentlyfrom a system outside the electric storage apparatus so as not todecrease to the level at which the engine cannot be started.

An electric storage apparatus described herein includes an outputterminal configured to be electrically connected to a system includingan engine, an electric storage device, a monitoring apparatus includinga detector and a controller, and a relay disposed between the outputterminal and the electric storage device. The detector is configured todetect a variation value corresponding to an amount of charge of theelectric storage device. The controller is configured to determinewhether the variation value detected by the detector is equal to orlower than an opening threshold, and execute an opening process toswitch a state of the relay from a closed state to an open state if thevariation value is equal to or lower than the opening threshold. Theopening threshold is larger than an engine activation low-threshold by apredetermined value. The engine activation low-threshold is a lowestlevel of the amount of charge at which the engine is able to be started.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features of the present invention will becomeapparent from the following description and drawings of an illustrativeembodiment of the invention in which:

FIG. 1 is a configuration diagram of a battery according to anembodiment, an on-vehicle device, and other devices;

FIG. 2A is a flowchart of a power control process;

FIG. 2B is a flowchart of an activation process; and

FIG. 3 is a graph illustrating SOC-OCV characteristics of an ironphosphate lithium ion battery.

DESCRIPTION OF EMBODIMENTS

According to a first aspect of the present invention, an electricstorage apparatus includes an output terminal to be electricallyconnected to a system including an engine, an electric storage device, amonitoring apparatus including a detector and a controller, and a relaydisposed between the output terminal and the electric storage device.The detector is configured to detect a variation value corresponding toan amount of charge of the electric storage device. The controller isconfigured to determine whether the variation value detected by thedetector is equal to or lower than an opening threshold, and execute anopening process to switch a state of the relay from a closed state to anopen state if the variation value is equal to or lower than the openingthreshold. The opening threshold is larger than an engine activationlow-threshold by a predetermined value. The engine activationlow-threshold is a lowest level of the amount of charge at which theengine is able to be started.

The electric storage apparatus according to this aspect includes therelay. The relay in the closed state is switched to the open state whenthe controller determines that the variation value corresponding to theamount of charge of the electric storage device is equal to or lowerthan the opening threshold. With this configuration, the electricstorage apparatus itself can control the amount of charge thereofindependently from a system outside the electric storage apparatus so asnot to decrease to the level at which the engine cannot be started.

According to a second aspect of the present invention, in theabove-described electric storage apparatus, the controller is furtherconfigured to switch a power consumption mode of the monitoringapparatus between a first power consumption mode, in which themonitoring apparatus monitors the electric storage device, and a secondpower consumption mode, in which the monitoring apparatus consumes lesspower supplied from the electric storage device than in the first powerconsumption mode, determine whether the variation value detected by thedetector is lower than a low power threshold, and execute a power savingprocess to switch the power consumption mode of the monitoring apparatusfrom the first power consumption mode to the second consumption state ifthe variation value is equal to or lower than the low power threshold.In the first power consumption mode, the monitoring apparatus monitorsthe electric storage device. In the second power consumption mode, themonitoring apparatus consumes less power supplied from the electricstorage device than in the second power consumption mode. With thisconfiguration, the monitoring apparatus consumes less power of theelectric storage device.

According to a third aspect of the present invention, theabove-described electric storage apparatus further includes a receiverthat is configured to receive a return instruction based on an externalinput. The controller is configured to execute a return process toswitch the power consumption mode of the monitoring apparatus from thesecond power consumption mode back to the first power consumption modeif the receiver receives the return instruction. With thisconfiguration, the monitoring apparatus can monitor the electric storagedevice again.

According to a fourth aspect of the present invention, in theabove-described electric storage apparatus, the controller is configuredto execute a closing process to switch the state of the relay from theopen state back to the closed state if the controller executes thereturn process to switch the power consumption mode of the monitoringapparatus back to the first power consumption mode. With thisconfiguration, the power of the electric storage device can be suppliedto the engine again.

According to a fifth aspect of the present invention, in theabove-described electric storage apparatus, the controller is configuredto determine whether the engine is started in a period between when thestate of the relay is switched back to the closed state and whenreference closing time is completed, and execute a re-opening process toswitch the state of the relay from the closed state to the open stateagain if the start of the engine is not determined.

The charge of the electric storage device starts when the engine isstarted. However, if a condition in which the engine is not startedcontinues after the state of the relay is switched back to the closedstate, the power provided by the electric storage device is consumed bythe electric load because the relay is in the closed state, and thus theamount of charge of the electric storage device decreases to the levelat which the engine cannot be started. To solve this problem, in theelectric storage apparatus, the state of the relay is switched back tothe open state if the controller determines that the engine is notstarted in the period between when the state of the relay is switchedback to the closed state and when the reference closing time iscompleted. With this configuration, the power provided by the electricstorage device is less likely to be continuously consumed by theelectric load because the relay does not remain in the closed state fora long time while the engine is not started after the relay is switchedback to the closed state.

According to a sixth aspect of the present invention, in theabove-described electric storage apparatus, the controller is furtherconfigured to determine whether the engine is started in a periodbetween when the power consumption mode is switched back to the firstpower consumption mode and when reference power time is completed, andexecute a re-power saving process to switch the power consumption modeof the monitoring apparatus back to the second power consumption mode ifthe start of the engine is not determined. In this configuration, acondition in which the engine is not started for a long time after thepower consumption mode of the monitoring apparatus is back in the firstpower consumption mode does not continue, and thus the power of theelectric storage device may not be consumed by the controller in thefirst power consumption mode.

According to a seventh aspect of the present invention, in theabove-described electric storage apparatus, the controller is configuredto determine whether a voltage of the electric storage device exceeds anovercharge threshold based on the variation value detected by thedetector, and execute an overcharge protection process to switch thestate of the relay from the closed state to the open state if thevoltage of the electric storage device exceeds the overcharge threshold.With this configuration, the relay can be used to prevent overcharge.

The technologies described herein can be used in various applicationsincluding an electric storage apparatus, a power control method of anelectric storage apparatus, a computer program for executing thefunction of the apparatus or the method, or a recording medium thatstores the computer program.

According to the technology described herein, the electric storageapparatus is configured to control the amount of charge thereofindependently from a system outside the electric storage apparatus so asnot to decrease to the level at which the engine cannot be started.

An embodiment will be described with reference to FIG. 1 to FIG. 3.

As illustrated in FIG. 1, a battery 1 according to this embodiment is astarter battery that supplies power to a starter 3 to start an engine 2.The battery 1 is installed in a vehicle such as an engine vehicle or ahybrid vehicle. The battery 1 also supplies power to an engine controlunit (hereinafter, referred to as an ECU) 4, and an on-vehicle device 5such as a clock, a light, an audio system, or a security system. Thebattery 1 is charged by an alternator 6 that generates power using therotation of the engine 2. The battery 1 is an example of an electricstorage apparatus. The ECU 4 or the on-vehicle device 5 is an example ofan electric load.

Configuration of Battery

The battery 1 includes an assembled battery 11, a relay 12, a batterymanagement system (hereinafter, referred to as BMS) 13, and an outputterminal 14. The assembled battery 11 is an example of an electricstorage device. The assembled battery 11 includes cells C that areconnected in series. The cell C is a secondary battery that isrechargeable, specifically, an iron phosphate lithium ion battery thathas a graphite anode. In FIG. 1 and the description below, the assembledbattery 11 includes four cells C.

The starter 3, the ECU 4, the on-vehicle device 5, and the alternator 6are electrically connected to the output terminal 14. The relay 12 isprovided inside the battery 1 and is connected between the assembledbattery 11 and the output terminal 14. The state of the relay 12 isswitched between an open state and a closed state by an opening orclosing control of a controller 22, which will be described later. Therelay 12 is a latching relay. Once the relay 12 is set in the open stateor the closed state through an instruction from the controller 22, theopen state or the closed state is maintained even when the power supplyis stopped. In the closed state of the relay 12, the battery 1 cansupply power to the starter 3, the ECU 4, or the on-vehicle device 5,and the battery 1 can be charged by the alternator 6. In the open stateof the relay 12, the battery 1 cannot supply power to the starter 3 andthe others, and the battery 1 cannot be charged by the alternator 6.

The BMS 13 includes a voltage detection circuit 21, the controller 22,an activation switch 23, a communication unit 24, and four equalizationcircuits (discharge circuits) 25. The BMS 13 is an example of amonitoring apparatus. The voltage detection circuit 21 is an example ofa detector. The voltage detection circuit 21 detects the voltage of eachcell C and transmits the detected voltage to the controller 22. Thevoltage detection circuit 21 may be configured to detect a voltageacross the assembled battery 11. The BMS 13 may include other detectorsin addition to the voltage detection circuit 21. Examples thereofinclude a current detector that detects a current flowing through theassembled battery 11 and a temperature detector that detects atemperature of the assembled battery 11. The BMS 13 may be configured tomonitor states of the assembled battery 11 such as an internalresistance or a state of charge (hereinafter, referred to as SOC) basedon the detection results.

The controller 22 includes a central processing unit (hereinafter,referred to as a CPU) 22A and a memory 22B. The controller 22 and thevoltage detection circuit 21 are activated when power is supplied fromthe assembled battery 11. The controller 22 is configured to switch apower consumption mode of the BMS 13 among a normal mode, a sleep mode,and a deep sleep mode. In these modes, the BMS 13 consumes powersupplied by the assembled battery 11 at different levels. In otherwords, the controller 22 has a power saving function or a powerswitching function.

The normal mode is an example of a first power consumption mode of theBMS 13 while the vehicle is driving. In normal mode, the power issupplied from the assembled battery 11 to the voltage detection circuit21, the controller 22, and the communication unit 24. This enables theBMS 13 to monitor the state of the assembled battery 11 such as avoltage of the cell C.

The sleep mode is another example of the first power consumption mode ofthe BMS 13 in which the BMS 13 consumes less power than in normal mode.The BMS 13 is in this power consumption mode while the vehicle is parkedand the engine 2 is stopped. Like in the normal mode, in the sleep mode,the power is supplied from the assembled battery 11 to the voltagedetection circuit 21, the controller 22, and the communication unit 24.This enables the BMS 13 to monitor the state of the assembled battery11. However, in the sleep mode, the BMS 13 monitors the voltage of thecells C in a longer cycle than in the normal mode, for example, bylowering a clock frequency of the controller 22.

The deep sleep mode is an example of a second power consumption mode. Indeep sleep mode, the BMS 13 consumes much less power than in the sleepmode. In the deep sleep mode, the power is supplied from the assembledbattery 11 to none of the voltage detection circuit 21, the controller22, and the communication unit 24. This does not enable the BMS 13 tomonitor the state of the assembled battery 1.

The memory 22B stores various programs for controlling the operation ofthe controller 22 (including programs for executing a power controlprocess, which will be described later). The CPU 22A controls each unitof the controller 22 in accordance with the program that is read out ofthe memory 22B. The memory 22B includes RAM or ROM. Other than the RAMor the ROM, the programs may be stored in a non-volatile memory such asCD-ROM, a hard disc device, or a flush memory.

The activation switch 23 is an electrical switch such as an FET. Theswitch 23 applies activation signal SG1 to a built-in switch, which isnot illustrated, of the controller 22 based on an input through anoperation by the user. Upon receiving the activation signal SG1 whilethe power consumption mode is in the deep sleep mode, the controller 22turns on the built-in switch and the current starts to flow. Then, theassembled battery 11 starts to supply the power again and the powerconsumption mode of the BMS 13 is back in the normal mode or the sleepmode. In this embodiment, the activation switch 23 is an example of areceiver and the input through an operation by the user is an example ofexternal input.

The communication unit 24 receives signals SG2 to SG5, which will bedescribed later, from the ECU 4 and inputs the signals SG2 to SG5 to theCPU 22A. The equalization circuits 25 are connected in parallel to therespective cells C and each include a switching element 25A and adischarge resistance 25B. The controller 22 closes the switching element25A of each equalization circuit 25 to discharge the power of the cellC, which is connected in parallel to the equalization circuit 25,through the discharge resistance 25B.

Power Control Process

The controller 22 executes the power control process illustrated in FIG.2A when the power from the assembled battery 11 is supplied thereto. Thecontroller 22 determines whether the engine 2 is stopped (S1). The ECU 4transmits a lock signal SG3, an accessory signal SG4, an ignition-onsignal SG5, or an engine activation signal SG2 to the communication unit24 according to a position of an ignition switch, i.e., a lock position,an accessory position, an ignition-on position, or a start position,respectively.

The controller 22 determines that the engine 2 is stopped if the signalreceived by the communication unit 24 is the lock signal SG3 or theaccessory signal SG4. If the signal received by the communication unit24 after the engine activation signal SG2 is the ignition-on signal SG5,the controller 22 determines that the engine 2 is running. If thebattery 1 is installed in an idling stop vehicle, the engine 2 of whichis temporary stopped during driving, the controller 22 may be configuredto determine that the engine 2 is stopped or determine that the engine 2is running because the stop is temporary when the communication unit 24receives an engine temporary stop signal from the ECU 4.

(1) Processes while Engine is Running

If the engine 2 is running (NO in step S1), the controller 22 switchesthe power consumption mode of the BMS 13 to the normal mode (S2).Specifically, if the BMS 13 is in the normal mode, the controller 22maintains the normal mode, and if the BMS 13 is in another mode, thecontroller 22 switches the mode to the normal mode. In the normal mode,the relay 12 is usually in the closed state.

The ECU 4 executes a charge control if the SOC of the assembled battery11 decreases to the level that corresponds to a charge start SOC, atwhich the charging of the assembled battery 11 is started, while theengine 2 is running. In the charge control, the assembled battery 11 ischarged by the power generated by the alternator 6 and the charging endswhen the SOC reaches a level that corresponds to a charge stop SOC(about 99%). As illustrated in FIG. 3, in the iron phosphate lithium ionbattery, a region of about 75% to about 100% of SOC is a flat region(plateau) in which a change rate of an open circuit voltage(hereinafter, referred to as OCV) is relatively low, and it is difficultto accurately estimate an SOC from the OCV. In contract, a region ofabout 55% to 70% of SOC is a variation region in which the change rateof the OCV is higher than the flat region, and an SOC can be accuratelyestimated from the OCV. In this embodiment, the charge start SOC is setat about 60% (refer to a charge control region in FIG. 3).

The controller 22 executes an overcharge protection process (S3 to S6)after the controller 22 switches the power consumption mode of the BMS13 to the normal mode. In the overcharge protection process, based on adetection result of the voltage detection circuit 21, the controller 22determines whether a cell voltage Vc of at least one of the cells C ishigher than an overcharge threshold Vth2 (S3). If cell voltages Vc ofall the cells C are lower than the overcharge threshold Vth2 (NO in stepS3), the cells C are in a normal state, and the controller 22 returns tostep S1. If the controller 22 determines that the cell voltage Vc of atleast one of the cells C is equal to or higher than the overchargethreshold Vth2 (YES in step S3), the at least one cell C is in anovercharged state, and the controller 22 proceeds to the next overchargeprotection steps (S4 to S6).

The controller 22 switches the state of the relay 12 to the open stateto stop the charge by the alternator 6 (S4), and executes equalization(SS5). The controller 22 closes the switch element 25A of theequalization circuit 25 that is connected in parallel to the cell C thatis in the overcharged state to reduce the cell voltage Vc thereof to thesame level as the cell voltage Vc of the other cells C.

After the equalization, the controller 22 executes a return process toswitch the state of the relay 12 to the closed state again (S6). Then,the controller 22 returns to step S1. In this configuration, the relay12 can be used for the overcharge protection. The ECU 4 preferablysupplies the power generated by the alternator 6 to the on-vehicledevice 5 or other devices while the relay 12 is opened. The controller22 may execute the equalization (SS5) before step S4, or may not executethe equalization (S5).

(2) Processes while Engine is Stopped

In step S1, if the controller 22 determines that the engine 2 is stopped(YES in step S1), the controller 22 switches the power consumption modeof the BMS 13 to the sleep mode (S7). Specifically, if the BMS 13 is inthe sleep mode, the controller 22 maintains the sleep mode, and if theBMS 13 is in the other mode, the controller 22 switches the mode to thesleep mode. Like in the normal mode, in the sleep mode, the relay 12 isusually in the closed state. This allows the power supply from theassembled battery 11 to the on-vehicle device 5 or other devices, butthe assembled battery 11 is not charged. Accordingly, the SOC decreasesdue to self-discharge, power consumption by the BMS 13 or the on-vehicledevice 5, or the dark current.

In this step, variations in the cell voltages Vc of the cells C arerelatively small because the engine 2 is stopped and the BMS 13 is inthe sleep mode. Therefore, the cell voltages Vc are substantially inproportion to the OCV. Accordingly, the controller 22 can estimate theOCV or the SOC of each cell based on the cell voltage Vc of each cell C.

After the controller 22 switches the power consumption mode of the BMS13 to the sleep mode, based on the detection result of the voltagedetection circuit 21, the controller 22 determines whether the cellvoltage Vc of at least one of the cells C is equal to or lower than apower-saving threshold Vth1 (an example of a low power threshold and anopening threshold) (S8). The power-saving threshold Vth1 is larger thanan engine activation low-threshold Vth3. Specifically, the power-savingthreshold Vth1 is obtained by adding a predetermined value to the engineactivation low-threshold Vth3. The engine activation low-threshold Vth3is an OCV that corresponds to the lowest level of the SOC at which theengine 2 can be started (the lowest SOC). For example, the predeterminedvalue is less than 1.0 V, less than 0.5 V, or less than 0.1 V.

The controller 22 may be configured to determine whether the cellvoltage Vc of each of the cells C is equal to or lower than thepower-saving threshold Vth1, or whether a lowest cell voltage of thecell voltages Vc of the cells C is equal to or lower than thepower-saving threshold Vth1. The controller 22 may be configured todetermine whether the cell voltage Vc of at least one of the cells C isbetween the power-saving threshold Vth1 and the engine activationlow-threshold Vth3. In addition, the controller 22 may be configured todetermine whether the total voltage of the assembled battery 11 (thetotal of the cell voltages Vc of all the cells C), instead of the cellvoltage Vc of each cell C, is lower than the opening threshold in stepS8.

As indicated in FIG. 3, in an engine startable region (20% to 100% ofSOC) of the iron phosphate lithium ion battery, the region of about 40%to 50% of the SOC is the flat region, and the region of about 20% to 35%of the SOC is the variation region. The power-saving threshold Vth1 ispreferably set in this variation region. In this embodiment, thepower-saving threshold Vth1 is set at the OCV (about 3.28 V) thatcorresponds to about 30% of the SOC. Hereinafter, such an SOC isreferred to as the power saving SOC.

In step S8, if the controller 22 determines that the cell voltages Vc ofall the cells C are higher than the power-saving threshold Vth1 (NO instep S8), the SOC of each cell C is at a level at which the engine 2 canbe started. Then, the controller 22 returns to step S1. In contrast, ifthe controller 22 determines that the cell voltage Vc of at least one ofthe cells C is equal to or lower than the power-saving threshold Vth1(YES in step S8), the SOC of the cell C may be close to the lowest SOCat which the engine 2 cannot be started. Therefore, the controller 22switches the state of the relay 12 to the open state and switches thepower consumption mode of the BMS 13 to the deep sleep mode (S9).Accordingly, the power is not supplied from the assembled battery 11 tothe controller 22 and the communication unit 24.

In step S9, the timing of the opening of the relay 12 and the timing ofswitching the power consumption mode of the BMS 13 to the deep sleepmode may be or may not be the same. For example, the controller 22 mayswitch the power consumption mode of the BMS 13 to the deep sleep modeafter the opening of the relay 12.

When step S9 is performed, the power supply from the assembled battery11 to the on-vehicle device 5 or other devices stops. With thisconfiguration, the power consumption of the assembled battery 11 isreduced. As a result, after the cell voltage Vc becomes equal to orlower than the power saving threshold Vth1, the SOC of the cell Cdecreases toward the lowest SOC more slowly than that of a cell in abattery with a configuration in which step S9 is not performed. In otherwords, the SOCs of the cells C remain in the engine startable region fora longer period of time and the battery hardly runs out.

Since the ECU 4 executes the charge control as described above, the SOCof the assembled battery 11 is not always maintained at about 100%during the driving of the vehicle. In some cases, the SOC may decreaseto about 60% immediately after the engine 2 is stopped (refer to anengine stopped region in FIG. 3, in which a vehicle is parked).Accordingly, the battery 1 of this embodiment is particularly usefulcompared to the configuration in which the ECU 4 always charges theassembled battery 11 to full capacity during the driving of the vehicle.

Experiments were conducted under the following conditions: the powerconsumption of the assembled battery 11 due to the self-discharge wasabout 1 mA/day in terms of current; the power consumption of the BMS 13in the sleep mode was about 1 mA/day in terms of current; and the powerconsumption of the on-vehicle device 5 was about 15 mA/day in terms ofcurrent. Further, the SOC at the time when the engine 2 was stopped was60%, the SOC corresponding to the power-saving threshold Vth1 was 30%,and the lowest SOC was 20%. In a comparative example in which acontroller did not execute the processes in step S9, the SOC of the cellC decreased to the lowest SOC on 47th day after the engine 2 wasstopped. In contrast, the controller 22 of this embodiment executed stepS9 on about 35th day after the engine 2 was stopped, and then the SOC ofthe cell C decreased to the lowest SOC on about 114th day. As apparentfrom this example, the SOC of the cell C in this embodiment took alonger time to reach the lowest SOC by more than 100 days than thecomparative example without the processes in S9.

In the iron phosphate lithium ion battery, if the SOC of the cell C isin an engine unstartable region (for example, 0% to 20% of SOC, refer toFIG. 3), the battery goes dead, and if the SOC is lower than 0, thebattery may not be reused. Step S8 and step S9 are examples of theopening process and the power saving process. The SOC in the engineunstartable region or other regions differ depending on types of vehicleor environments.

If the activation switch 23 is turned on when the BMS 13 is in the deepsleep mode and the power is not supplied to the controller 22, thecurrent starts flowing through the controller 22 and the power issupplied from the assembled battery 11 to the controller 22 again. Thecontroller 22 executes an activation process illustrated in FIG. 2B. Theengine 2 is more likely to start shortly after the activation switch 23of the battery is turned on, and thus the controller 22 switches thestate of the relay 12 back to the closed state and switches the powerconsumption mode of the BMS 13 back to the sleep mode (S11).

In step S11, the timing of the closing the relay 12 and the timing ofthe switching back of the BMS 13 to the sleep mode may be or may not bethe same. For example, the controller 22 may switch the state of therelay 12 to the closed state after switching the power consumption modeof the BMS 13 back to the sleep mode.

The processes in step S11 allow the assembled battery 11 to be back inthe state that can supply the power to the on-vehicle device 5 and allowthe BMS 13 to be back in the state that can monitor the assembledbattery 11 before the engine 2 starts. In other words, even if the BMS13 is in the deep sleep mode and not monitoring the assembled battery11, upon receiving the return instruction, the BMS 13 can be back in thesleep mode or the other mode that can monitor the assembled battery 13.Accordingly, while the vehicle is parked, the BMS 13 can be in the deepsleep mode to reduce the power consumption without any problems.

Subsequently, the controller 22 determines whether the engine 2 isstarted in a period between when the mode of the BMS 13 is switched backto the sleep mode or the other mode and when waiting time (an example ofreference closing time or reference power time) is completed (S12). Ifthe controller 22 receives the engine activation signal SG2 before thewaiting time is completed, the controller 22 determines that the engine2 is started (YES in step 12) and the controller 22 returns to step S1in FIG. 2A. Then, the controller 22 proceeds to step S2, and thus theassembled battery 11 is charged by the alternator 6.

If the controller 22 does not receive the engine activation signal SG2by the end of the waiting time, the controller 22 determines that theengine 2 is not started (NO in step S12). The controller 22 switches thestate of the relay 12 to the open state again and switches the powerconsumption mode of the BMS 13 to the deep sleep mode again (S13). Withthis configuration, the power provided by the assembled battery 11 isless likely to be continuously consumed by the on-vehicle device 5 orthe BMS 13 because the relay 12 does not remain in the closed state fora long time while the engine 2 is not started after the relay 12 isswitched back to the closed state. Therefore, the battery 1 is lesslikely to be dead.

Effects

According to this embodiment, the battery 1 includes the relay 12 andthe BMS 13 therein in addition to the assembled battery 11. The BMS 13controls the opening and the closing of the relay 12. With thisconfiguration, the battery 1 can control itself independently fromsystems installed in a vehicle body, i.e., systems other than BMS 13 inthe vehicle, so as not to run out. In comparison to a configuration inwhich the relay 12 is provided in anywhere in the vehicle other thaninside the battery 1, the relay 12 is less likely to be out of controldue to communication errors between the battery 1 and the other system.

OTHER EMBODIMENTS

The present invention is not limited to the embodiment described aboveand illustrated in the drawings. The following various embodiments arealso included in the technical scope of the present invention.

The electric storage device is not limited to the electric storagedevice that includes the cells connected in series, but may be anelectric storage device that includes cells connected in parallel. Thenumber of the cells may suitably be changed. The electric storage deviceis not limited to the assembled battery 11, but may include a singlecell. The electric storage device is not limited to the iron phosphatelithium ion battery that has a graphite anode. The electric storagedevice may be other non-aqueous electrolyte secondary batteries such asa manganese lithium ion battery, or other batteries than the non-aqueouselectrolyte secondary battery such as a lead electric storage battery ora nickel metal hydride battery. Further, the electric storage device isnot limited to the secondary battery, but may be a capacitor. Theelectric storage device may be any battery that is used to start anengine of a machine provided with an engine (internal combustion engine,for example) as a driving source. For example, the machine may be anaircraft or a machine tool in addition to the vehicle.

The second power consumption mode may be a mode in which the assembledbattery 11 supplies the power to at least one of the voltage detectioncircuit 21, the controller 22, and the communication unit 24. Forexample, in the deep sleep mode, the power may be supplied to thecontroller 22 and the communication unit 24, and the power may not besupplied to the voltage detection circuit 21. In such a case, thecontroller 22 may stop the monitoring of the voltage of the cell C andstop the opening or closing of the relay 12, and may be only capable ofdetermining whether the communication unit 24 receives the input signalfrom outside. The controller 22 may switch the power consumption mode ofthe BMS 13 back to the sleep mode or the normal mode when thecommunication unit 24 receives the input signal.

Specifically, if the power is supplied from a power source other thanthe assembled battery 11 to the ECU 4 and the ECU 4 can output thesignals such as the ignition-on signal SG5 to the communication unit 24with the relay 12 in the open state, the controller 22 can determinethat the return instruction is received when the communication unit 24receives the ignition-on signal SG5. The engine 2 is more likely tostart when a driver turns the ignition switch to the ignition-onposition. In this configuration, the communication unit 24 is an exampleof a receiver. The communication unit 24 may be configured to receivethe return instruction via wire communication or via wirelesscommunication. For example, the communication unit 24 may be configuredto receive the return instruction based on radio transmissions from aremote control switch operated by the driver. The controller 22 maydetermine that the return instruction is received upon receiving theaccessory signal SG4.

In the above configuration in which the power can be supplied to thecontroller 22 and the communication unit 22 in the deep sleep mode, instep S9, the controller 22 may switch the state of the relay 12 to theopen state after the controller 22 switches the power consumption modeof the BMS 13 to the deep sleep mode. Further, in step S11, thecontroller 22 may switch the power consumption mode of the BMS 13 backto the sleep mode or the normal mode after the controller 22 switchesthe state of the relay 12 back to the closed state.

In the above configuration in which the power can be supplied to thecontroller 22 and the communication unit 22 in the deep sleep mode, thewaiting time may be set longer for the case where the controller 22receives the activation signal SG1 than for the case where thecontroller 22 receives the ignition-on signal SG5 or the accessorysignal SG4. This is based on the assumption that a longer time isrequired if the controller 22 receives the activation signal SG1,because, after turning on the activation switch 23 of the battery 1, thedriver needs to come back from the position where the battery 1 isinstalled to the driver's seat to turn the ignition switch to the startposition.

As described above, the receiver may be configured to receive the returninstruction based on the input signal from the communication unit 24, ormay be configured to receive the return instruction based on thehuman-operated input using the activation switch 23. The activationswitch 23 may be a mechanical switch and may be configured to beswitched between the open state and closed state by an operation of theuser. When the activation switch 23 is switched to the closed state, thepower starts to be supplied from the assembled battery 11 to thecontroller 22 again, and the power consumption mode of the BMS 13 isswitched back to the normal mode or the sleep mode.

In the above embodiment, the controller 22 including one CPU 22A and thememory 22B is described as an example of a controller. However, thecontroller is not limited to this. The controller may include aplurality of CPUs or may include a hard circuit such as an ASIC(Application Specific Integrated Circuit) or may include both of thehard circuit and the CPU. For example, the controller may execute someprocesses or all of the processes of the power control process bydifferent CPUs or hard circuits. The order of the steps in FIGS. 2A, 2Bmay be suitably changed.

In the above embodiment, the low power threshold or the openingthreshold are the same power-saving threshold Vth1. However, the presenttechnology is not limited to this. The low power threshold and theopening threshold may differ from each other. Specifically, in step S8and step S9, the controller 22 may compare the cell voltage Vc of eachcell C to the opening threshold in addition to the power-savingthreshold Vth1. The controller 22 may be configured to switch the powerconsumption mode of the BMS 13 to the deep sleep mode when determiningthat at least one of the cells C has the cell voltage Vc that is lowerthan the power-saving threshold Vth1, and to switch the state of therelay 12 to the open state when determining that at least one of thecells C has the cell voltage Vc that is lower than the openingthreshold.

In the above embodiment, the reference closing time and the referencepower time are the same waiting time. However, the present technology isnot limited to this. The reference closing time and the reference powertime may differ from each other. Specifically, in step S12 and step S13,the controller 22 may determine whether a first waiting time and asecond waiting time that are different from each other elapse from thetime when the BMS 13 is back in the sleep mode or the other mode. If thecontroller 22 determines that the engine 2 does not start by the end ofthe first waiting time, the controller 22 may switch the state of therelay 12 to the open state again. If the controller 22 determines thatthe engine 2 does not start by the end of the second waiting time, thecontroller 22 may switch the power consumption mode of the BMS 13 to thedeep sleep mode again.

The controller 22 may be configured to determine whether the engine 2 isstopped based on the voltage or the current of the assembled battery 11in step S1. For example, the controller 22 may determine that the engine2 is stopped if the controller 22 determines that a variation amount ofthe voltage of the assembled battery 11 continues to be lower than areference value for a predetermined time.

In the above embodiment, in S8 or other steps, the controller 22determines about the SOC based on the voltage Vc of the cell C. However,the present technology is not limited to this. The controller 22 maydetermine about the SOC based on a variable element that has acorrelation with the SOC. For example, the variable element is a currentaccumulated amount that is obtained by integrating charge and dischargecurrents over time. In other words, the controller 22 may have anyconfiguration that can execute the process in step S8 based on thevariation value corresponding to the amount of charge of the assembledbattery 11.

The controller 22 may not be configured to switch the power consumptionmode of the BMS 13 to the sleep mode in step S9. Even in such aconfiguration, the BMS 13 consumes less power of the assembled battery11.

What is claimed is:
 1. A battery, comprising: an output terminal; anelectric storage device; a relay connected to the output terminal andthe electric storage device; and a monitoring apparatus including adetector and a controller, the detector being configured to detect avariation value corresponding to an amount of charge of the electricstorage device, the controller receiving an engine activation signal andswitching a state of the relay to a closed state, wherein, if an engineis not started, the controller switches the state of the relay to anopen state.
 2. The battery according to claim 1, further comprising: acommunication unit connected to the controller and receiving an inputsignal from outside, wherein the controller is configured to execute areturn process to switch on a power supply route in the electric storageapparatus if the communication unit receives a return instruction basedon the input signal.
 3. The battery according to claim 2, wherein thecommunication unit is configured to receive the return instruction basedon a remote transmission from a remote control switch.
 4. The batteryaccording to claim 2, wherein the communication unit is configured toreceive the return instruction based on an ignition-on signal.
 5. Thebattery according to claim 1, wherein the controller is configured toswitch a power consumption mode between a first power consumption mode,in which the monitoring apparatus monitors the electric storage device,and a second power consumption mode, in which the monitoring apparatusconsumes less power supplied from the electric storage device than inthe first power consumption mode.
 6. The battery according to claim 5,wherein the controller is further configured to execute a power savingto switch the power consumption mode of the monitoring apparatus fromthe first power consumption mode to the second consumption mode based ona comparison of the variation value to a power threshold.
 7. The batteryaccording to claim 6, wherein the controller is further configured toswitch the power consumption mode of the monitoring apparatus from thesecond power consumption mode back to the first power consumption modeif a communication unit of the battery receives a return instructionbased on an input signal from outside.
 8. The battery according to claim5, wherein the controller is further configured to determine whether theengine is started in a period between when the power consumption mode isswitched back to the first power consumption mode and when a referencepower time is completed.
 9. The battery according to claim 8, whereinthe controller is further configured to execute a re-power savingprocess to switch the power consumption mode of the monitoring apparatusback to the second power consumption mode if the engine is determined tonot be started.
 10. The battery according to claim 1, wherein thecontroller is configured to determine whether the engine is started in aperiod between when a state of the relay is switched back to the closedstate and when a reference closing time is completed.
 11. The batteryaccording to claim 10, wherein the controller is further configured toexecute a re-opening process to switch the state of the relay from theclosed state to the open state if the engine is determined to not bestarted.
 12. The battery according to claim 1, wherein the controller isconfigured to determine whether a voltage of the electric storage deviceexceeds an overcharge threshold based on the variation value detected bythe detector.
 13. The battery according to claim 12, wherein thecontroller is further configured to execute an overcharge protectionprocess to switch the state of the relay from the closed state to theopen state if the voltage of the electric storage device exceeds theovercharge threshold.
 14. The battery according to claim 1, wherein theelectric storage device comprises an iron phosphate lithium ion batterythat includes a graphite anode.
 15. The battery according to claim 1,wherein the relay comprises a latching relay.
 16. The battery accordingto claim 1, wherein the detector includes: a voltage detection circuitthat detects a voltage of the electric storage device; and a currentdetector that detects a current flowing through the electric storagedevice.
 17. The battery according to claim 16, wherein the detectorfurther includes: a temperature detector that detects a temperature ofthe electric storage device.
 18. The battery according to claim 1,further comprising a receiver configured to receive a return instructionbased on a remote transmission from a remote control switch, wherein thecontroller is configured to execute a return process to switch the stateof the relay from the open state back to the closed state if thereceiver receives the return instruction.
 19. An energy storageapparatus, comprising: an output terminal; an electric storage device; arelay connected to the output terminal and the electric storage device;a detector configured to detect a variation value corresponding to anamount of charge of the electric storage device; and a controller,depending upon an engine activation signal that indicates whether anengine is started, configured to switch a state of the relay between aclosed state and open state.
 20. A power control method of an electricstorage apparatus that includes an output terminal, an electric storagedevice, and a relay connected to the output terminal and the electricstorage device, the method comprising: detecting a variation valuecorresponding to an amount of charge of the electric storage device; andreceiving an engine activation signal that indicates whether an engineis started, and switching a state of the relay to a closed state,wherein, if an engine is not started, the state of the relay is switchedto an open state.